Implantable markers have been used to identify locations within objects, such as a human body. For example, a marker may be implanted in a patient within an organ of interest. As the patient moves, the marker can be used to track the location of the organ. Various techniques have been used to identify the location of such markers. For example, one technique requires a person to move a sensor over the area above the marker. When the sensor is positioned directly over the marker, the person may be given a visual or audio indication. A difficulty with such a technique for identifying a marker location is it does not provide the actual location of the marker (e.g., x, y, and z coordinates) and may not have the needed degree of accuracy.
One technique has been described for locating a source of an electrical signal within the brain by sensing the magnetic field generated by an electrical signal. This technique relies on a probability distribution to help identify the location of the source. A difficulty with such a technique is it may not have the needed degree of accuracy.
It would be desirable to have a technique for locating an implantable marker in real time and in the needed degree of accuracy.